CEEN 341 - Lecture 19 - Intro to Shear Strength and the Direct Shear Test

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  • Опубліковано 14 чер 2024
  • This lecture introduces the basic concepts of shear strength of soil. Soil friction is described, and the friction angle is derived. The Mohr-Coulomb failure criteria are introduced, which state that soil shear strength is a combination of cohesion and friction. The direct shear test is introduced and explained. An an example calculation with the direct shear test is performed to develop a Mohr-Coulomb failure envelope.
    Learning Objectives:
    1) Derive and/or explain what the the friction angle is in the soil.
    2) Derive the Mohr-Coulomb equation for shear stress in the soil, and explain when failure occurs in the soil.
    3) Explain the operation of the direct shear test and list some of its advantages and/or disadvantages.
    4) Using direct shear test results, compute the friction angle of a sand.
    Critical Questions to Consider:
    1) What are the two sources to soil shear strength?
    2) Why can't a Mohr circle ever cross the Mohr-Coulomb failure envelope? What happens once a point on the circle touches the envelope? How does the point of tangency where the Mohr circle touches the failure envelope relate to the orientation of the failure plane in the soil?
    3) What are some advantages and disadvantages of the direct shear test?
    4) What does it mean for a shear test to be a "drained" shear test? How do you think this would differ from an "undrained" shear test, which we will talk about in the next lecture or two?

КОМЕНТАРІ • 44

  • @ngonidzashekimbini7177
    @ngonidzashekimbini7177 2 роки тому

    Hands down best Geotech lecturer on YT😎.....THANK YOU

  • @ahmedtaha9731
    @ahmedtaha9731 6 років тому +1

    Thank you so much for posting your excellent lectures on UA-cam. Regards from Saudi Arabai.

  • @marshmelows
    @marshmelows 4 роки тому +3

    Great presentation indeed, love your diction and rhythm while presenting!

  • @ronaldlake767
    @ronaldlake767 6 років тому

    Fantastic lecture! Thank you Dr Franke!!

  • @bamispeciaal1
    @bamispeciaal1 5 років тому

    Great presentation. Thank you professor Franke!

  • @lbd1co
    @lbd1co 3 роки тому +1

    Wow! Thank you so much!! I have been struggling so much until I found your lectures. I really appreciate your efforts to make these complex concepts accessible to students from different backgrounds, learning pace and and learning style. Thank you!!

  • @alideep9656
    @alideep9656 6 місяців тому

    Thank you so much, that's a lot of valuable knowledge

  • @josecohen516
    @josecohen516 4 роки тому +2

    You're the man, thanks from Canada :)

  • @hassammajid8472
    @hassammajid8472 25 днів тому

    excellent sir ,plz complete the whole course your lectures are very amazing

  • @vikramjoshi3452
    @vikramjoshi3452 2 роки тому

    Amazing! God bless you!

  • @estebanmunoz7486
    @estebanmunoz7486 5 років тому

    Great lecture. Thanks

  • @saurovbarman4515
    @saurovbarman4515 2 роки тому

    Awesome and interesting!

  • @israrullah3398
    @israrullah3398 6 років тому

    thank you professor for the lectures.

  • @rubencastaneda8873
    @rubencastaneda8873 Рік тому

    Fantastic lectures!!!

  • @feliciamichael5916
    @feliciamichael5916 4 роки тому

    Thank you for the explanation

  • @kyawmyohtet4715
    @kyawmyohtet4715 6 місяців тому

    Cant pity myself enough. I just found out this lecture in a few days to graduate.

  • @rossanaherrera7018
    @rossanaherrera7018 6 років тому +2

    Thank you so much Dr. Franke. The lecture is very clear. I am writing from Peru

    • @jcoc8129
      @jcoc8129 11 місяців тому

      Creí que era el único peruano viéndolo

  • @mrwwang6233
    @mrwwang6233 5 років тому

    very good!!!

  • @lisro21
    @lisro21 7 років тому +6

    Do you by any chance have a foundation design or earth structures lecture videos. I am studying for the FE and was looking for material. Your lecture videos are great and detailed.

  • @srinivasamurthy9599
    @srinivasamurthy9599 6 років тому +3

    The way you explain the concepts is outstanding, sir. thanks a lot regards form INDIA

  • @kingshukmukherjee5789
    @kingshukmukherjee5789 2 роки тому +1

    Thank you so much sir!! I couldn't grasp the concepts and had literally lost complete interest in soil mechanics course of my curriculum. But your videos have been extremely helpful . Thanks a lot sir!!!

  • @phebomoralestapel5348
    @phebomoralestapel5348 4 роки тому

    Thank you Sir. 😊

  • @TDKMrDK
    @TDKMrDK 4 роки тому

    Thanks so much for your great sharing

  • @AbhishekPandey-uu7in
    @AbhishekPandey-uu7in 4 роки тому

    Great presentation n explanation sir

  • @inzimamurrehman2327
    @inzimamurrehman2327 3 роки тому

    great lectures

  • @monitoramentogeotecnico15
    @monitoramentogeotecnico15 3 роки тому +1

    Greetings from Brazil.
    Thanks for sharing your extraordinary lectures, dr. Franke.
    About the DSS test, why it cant be used for fiding undrained strengh?
    I would like to know a little bit more about the limitations of DSS test.

    • @officehours4028
      @officehours4028  2 роки тому +2

      The direct shear device (DS) does not have a membrane surrounding the soil, and therefore cannot be used to perform undrained tests. On the other hand, the direct simple shear device (DSS) DOES have a membrane and is capable of performing undrained tests. Perhaps you mistook my refence to the DS test as the DSS test.

  • @keleniengaluafe2600
    @keleniengaluafe2600 5 місяців тому

    ❤❤❤❤

  • @mahbubn
    @mahbubn 10 місяців тому

    Dear Professor, Thanks for your great effort.
    I have mailed to you extending my greetings.
    I think you are so busy to answer.
    Anyway, I wish you will continue your great work to enrich our knowledge with your lectures.

  • @thenineminus1
    @thenineminus1 6 років тому +1

    Does anyone understand how the angle Professor Franke found on 20:11? I don't understand why.

    • @mehulkatakiya4892
      @mehulkatakiya4892 5 років тому

      an external angle at any corner with an extension of a line will be a summation of two other angles of the triangle.

    • @rayoaklight
      @rayoaklight 5 років тому

      two radius of the circle therefore the triangle has two equal corners (0cr) . then the external angle 180-(180-20cr)

  • @matkontakos924
    @matkontakos924 3 роки тому

    Hi prof, im really into geotechnics but it's quite hard to really understand the concentps.Could you be more specific about the symmetrie of mohr-coulomb criteria,the symmetrie means that the element fails at to planes? one above and one below? or at one only and the direction is govern by the nature of the element?

    • @officehours4028
      @officehours4028  2 роки тому

      By definition, a circle is symmetric. Mohr's circles are symmetric about their center. For simple loading assumptions, the stresses that define the circle are symmetric on both sides of the sigma axis (i.e., the x-axis). In advanced soil mechanics, you will learn that the failure envelope is also "sort-of" symmetric about the sigma axis, meaning that there is a failure envelope on the negative side of the sigma axis that represents the failure state for tension. It has a different friction angle than the failure envelope for compression though, so it's not really symmetric.

  • @mehulkatakiya4892
    @mehulkatakiya4892 5 років тому

    at 43:28, while calculating tau, a contact area between soil decrease. shouldn't we consider?

    • @officehours4028
      @officehours4028  5 років тому +1

      You could, but the change in area is small enough and its effect is negligible such that most engineers ignore it.

    • @mehulkatakiya4892
      @mehulkatakiya4892 5 років тому +1

      @@officehours4028 but even if sample get failed at a displacement of 0.5 cm..then reduction in area is 3 sq.cm. if we are using 6 cm * 6 cm box..i think which is considerable..but yeah..considering full area will give us conservative results..lower tau and lower phi..👍..thank you.😊

  • @RaghunandanReddyC
    @RaghunandanReddyC 3 роки тому +2

    3:00 That house is horrified.